DISTURB-RESISTANT NON-VOLATILE MEMORY DEVICE AND METHOD
A disturb-resistant nonvolatile memory device includes a substrate, a dielectric material overlying the semiconductor substrate, a first cell comprising a first wiring structure extending in a first direction overlying the dielectric material, a first contact region, a first resistive switching media, and a second wiring structure extending in a second direction orthogonal to the first direction, a second cell comprising the first wiring structure, a second contact region, a second resistive switching media, and a third wiring structure separated from the second wiring structure and parallel to the second wiring structure, and a dielectric material disposed at least in a region between the first switching region and the second switching region to electrically and physically isolate the first switching region and the second switching region.
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The present invention claims priority to and is a continuation of U.S. application Ser. No. 13/733,828, filed Jan. 3, 2013 which claims priority to and is a divisional of U.S. application Ser. No. 12/861,666, filed Aug. 23, 2010. Those applications are herein incorporated by reference for all purposes.
BACKGROUNDThe present invention is generally related to resistive switching devices. More particularly, embodiments according to the present invention provide a method and a structure for forming a vertical resistive switching device. The present invention can be applied to non-volatile memory devices but it should be recognized that the present invention can have a much broader range of applicability
The success of semiconductor devices has been mainly driven by an intensive transistor down-scaling process. However, as field effect transistors (FET) approach sizes less than 100 nm problems such as short channel effect can degrade device performance. Moreover, such sub 100 nm device size can lead to sub-threshold slope non-scaling and also increases power dissipation. It is generally believed that transistor-based memories such as those commonly known as Flash may approach an end to scaling within a decade. Flash memory is one type of non-volatile memory device.
Other non-volatile random access memory (RAM) devices such as ferroelectric RAM (Fe RAM), magneto-resistive RAM (MRAM), organic RAM (ORAM), and phase change RAM (PCRAM), among others, have been explored as next generation memory devices. These devices often require new materials and device structures to couple with silicon-based devices to form a memory cell, which lack one or more key attributes. For example, Fe-RAM and MRAM devices have fast switching characteristics and good programming endurance, but their fabrication is not CMOS compatible and size is usually large. Power dissipation during switching for a PCRAM device is usually large. Organic RAM or ORAM is incompatible w large volume silicon-based fabrication and device reliability is usually poor.
From the above, a new semiconductor device structure and integration is desirable.
BRIEF SUMMARY OF THE PRESENT INVENTIONThe present invention is directed to switching devices. More particularly, embodiments according to the present invention provide a method and a structure to form an array of switching devices. The present invention has be applied to forming a disturb-resistant non-volatile memory device using an amorphous silicon switching material. But it should be recognized that embodiments of the present invention can be applied to other devices.
In a specific embodiment, a method of forming a disturb-resistant non-volatile memory device is provided. The method includes providing a substrate having a surface region and forming a first dielectric material overlying the surface region of the substrate. A first wiring material is formed overlying the first dielectric material and a contact material comprising a p+ doped polysilicon material is formed overlying the first wiring material. The method forms a switching material comprising an amorphous silicon material overlying the contact material. In a specific embodiment, the method includes subjecting the switching material to a first pattering and etching process to separating a first strip of switching material from a second strip of switching material. The first strip of switching material and the second strip of switching material are spatially oriented in a first direction in a specific embodiment. The method then subjects the first strip of switching material, the second strip of switching material, the contact material, and the first wiring material to a second patterning and etching process. The second patterning and etching process cause formation of at least a first switching element from the first strip of switching material and at least a second switching element from the second strip of switching material, and a first wiring structure comprising at least the first wiring material and the contact material. In a specific embodiment, the first wiring structure is configured to extend in a second direction at an angle to the first direction.
In a specific embodiment, a method of forming a disturb-resistant non volatile memory device is provided. The method includes providing a first cell and a second cell. The first cell includes a first wiring structure, a second wiring structure, a contact material overlying the first wiring structure and a switching material overlying the contact material. In a specific embodiment, the first wiring structure is configured to extend in a first direction and a second wiring structure extending in a second direction orthogonal to the first direction. In a specific embodiment, the switching material includes an amorphous silicon material and the contact material comprising a p+ polysilicon material In a specific embodiment, the first cell includes a first switching region formed in an intersecting region between the first wiring structure and the second wiring structure and a contact region between the switching first wiring structure and the switching region. In a specific embodiment, the second cell is formed from the first wiring structure, the switching material, the contact material, and a third wiring structure. The third wiring structure is configured parallel to the second wiring structure in a specific embodiment. A second switching region is formed in an intersecting region between the first wiring structure and the third wiring structure. In a specific embodiment, at least the switching material forms a coupling between the first cell and the second cell. In a specific embodiment, the coupling is eliminated at least by removing a portion of the switching material to form a void region. The void region is filled using a dielectric material to electrically and physically isolate at least the first switching region and the second switching region. In other implementation, a first void region can further be formed between the first contact region and the second region. The dielectric material fills the void region and the first void region to electrically and physically isolate the first switching region form the second switching region, and to electrically and physically the first contact region from the second contact region in a specific embodiment.
In a specific embodiment, a non-volatile memory device is provided. The device includes a substrate having a surface region and a first dielectric material overlying the surface region of the semiconductor substrate. The device includes at least a first cell and a second cell. In a specific embodiment, the first cell includes a first wiring structure extending in a first direction overlying the first dielectric material. A first contact region overlies the first wiring structure and a first switching region overlies the first contact region. The first contact region includes a p+ polysilicon material and the first switching region includes an amorphous silicon material in a specific embodiment. The first cell includes a second wiring structure extending in a second direction orthogonal to the first direction overlying the switching region. The second cell includes a second contact region comprising the p+ polysilicon material overlying the first wiring structure. A second switching region comprising the amorphous silicon material overlies the second contact region. The second cell includes a third wiring structure overlying the second switching region. The third wiring structure is separated from the second wiring structure and parallel to the second wiring structure. In a specific embodiment, a dielectric material is disposed at least in a region between the first switching region and the second switching region to electrically and physically isolate the first switching region and the second switching region. In other embodiment, the dielectric material is further disposed between a first region between the first contact region and the second contact region to further electrically and physically isolate the first contact region and the second region.
Many benefits can be achieved by ways of present invention. The present invention uses convention CMOS fabrication techniques to form a disturb resistant non-volatile memory array. Embodiments according to the present invention further provide an array of interconnected switching devices to be used in a high density memory device. Depending on the embodiment, one or more of these benefits can be achieved. One skilled in the art would recognize other variations, modifications, and alternatives.
The present invention is generally related to switching devices. More particularly, embodiments according to the present invention provide a method and a structure to form an array of switching devices. The present invention has be applied to forming a disturb resistant non-volatile memory device using an amorphous silicon switching material. But it should be recognized that embodiments of the present invention can be applied to other devices.
Embodiments of the present invention provide a method and a structure to form non-volatile memory device having a silver/amorphous silicon material/bottom electrode configuration. The present method and structure provide a device that is resistant to cross talk or disturb between adjacent cells in.
The method includes forming a first dielectric material 402 overlying the surface region of the substrate as shown in
Referring to
As shown
The method includes forming a switching material 702 overlying the contact material as shown in
In a specific embodiment, the method includes subjects the at silicon material to a first pattern and etch process to form a plurality of strips of amorphous silicon material 802 as shown in
In a specific embodiment, a second pattern and etch process is performed to remove a stack of materials comprise of amorphous silicon material, a portion of the polysilicon material and a portion of the first wiring material to form a second opening region 902 as shown in
Referring to
Referring to
Referring to
Depending on the embodiment, there can be other variations. For example, as shown in
In a specific embodiment, a method of forming a non-volatile memory device is provided. The method includes providing a first cell and a second cell in an N by M array of interconnected crossbar structures. The first cell includes a first wiring structure extending in a first direction and a second wiring structure extending in a second direction. The first direction and the second direction are at angle to each other. In a specific embodiment, the first wiring structure is configured to be orthogonal to the second wiring structure, forming a crossbar structure. In a specific embodiment, the first cell includes a contact material overlying the first wiring structure and a switching material overlying the contact material. In a specific embodiment, the contact material can be a p+ polysilicon material and the switching material can include an amorphous silicon material. The first call includes a first amorphous silicon switching region disposed in an intersecting region between the first wiring structure and the second wiring structure in a specific embodiment. In a specific embodiment, the second cell
In a specific embodiment, the second cell is formed from the first wiring structure, the switching material, the contact material, and a third wiring structure. The third wiring structure is parallel to the second wiring structure and separated from the second wiring structure in a specific embodiment. In a specific embodiment, a second switching region is dispose in an intersecting region between the first wiring structure and the third wiring structure. At least the switching material and the contact material form a coupling between the first cell and the second cell. The coupling is eliminated by removing a portion of the switching material and the contact material to form a void region between the first cell and the second cell. In a specific embodiment, the void region is filled using a dielectric material to electrically and physically isolate at least the first switching region and the second switching region. The dielectric material prevents disturb between the first cell and the second cell in a specific embodiment as illustrated in
In a specific embodiment, a non-volatile memory device is provided. The device includes a substrate having a surface region. A first dielectric material overlying the surface region of the semiconductor substrate. The device includes at least a first cell and a second cell. The first cell and the second cell are provided in an array of N by M interconnected crossbar structure in a specific embodiment. The first cell includes a first wiring structure extending in a first direction overlying the first dielectric material, a first contact region comprising a p+ polysilicon material, a first switching region comprising an amorphous silicon material, and a second wiring structure extending in a second direction orthogonal to the first direction in a specific embodiment. The second cell includes the first wiring structure, a second contact region comprising the p+ polysilicon material, a second switching region comprising the amorphous silicon material, and a third wiring structure. The third wiring structure is separated from the second wiring structure and spatially parallel to the second wiring structure in a specific Embodiment. In a specific embodiment, a dielectric material is disposed at least in a region between the first switching region and the second switching region to electrically and physically isolate at least the first switching region from the second switching region. The dielectric material prevents cross talk and disturbs between the first cell and the second cell when one of the cells is selected in each of the programming, writing, reading or erase cycles as illustrated in
Though the present invention has been described using various examples and embodiments, it is also understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or alternatives in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.
Claims
1. A device including a non-volatile memory device structure, comprising:
- a substrate having a surface region and comprising a plurality of transistors;
- a first dielectric material overlying the surface region of the semiconductor substrate;
- a first cell, the first cell comprising a first wiring structure extending in a first direction overlying the first dielectric material, a first buffer layer region comprising a p+ polycrystalline silicon containing material, a first switching region comprising an amorphous silicon material, and a second wiring structure extending in a second direction orthogonal to the first direction;
- a second cell, the second cell comprising the first wiring structure, a second buffer layer region comprising a p+ polycrystalline silicon containing material, a second switching region comprising an amorphous silicon material, and a third wiring structure separated from the second wiring structure and parallel to the second wiring structure; and
- a second dielectric material disposed at least in a region between the first switching region and the second switching region to electrically and physically isolate the first switching region and the second switching region;
- wherein at least one transistor from the plurality of transistors is coupled to the first cell.
2. The device of claim 1 wherein the first cell and the second cell are provided in an N by M interconnected crossbar array.
3. The device of claim 1 wherein the second dielectric material is further disposed in a first region between the first buffer layer region and the second buffer layer region, and in a second region between the second wiring structure and the third wiring structure.
4. The device of claim 1 further comprising:
- a third dielectric material having an upper surface disposed on top of the first switching region and the second switching region, wherein the third dielectric material comprises a first via in the upper surface exposing a portion of the first switching region, wherein the third dielectric material comprises a second via in the upper surface exposing a portion of the second switching region; and
- wherein the second wiring structure is coupled to the portion of the first switching region within the first via; and
- wherein the third wiring structure is coupled to the portion of the second switching region within the second via.
5. The device of claim 1
- wherein the first buffer layer region is coupled to the first wiring structure at a first region having a first lateral area;
- wherein the first switching region is coupled to the second wiring structure at a second region having a second lateral area; and
- wherein the first lateral area is different from the second lateral area.
6. The device of claim 1 wherein the plurality of transistors comprises a controller.
7. The device of claim 1 wherein the amorphous silicon material of the second cell and the amorphous silicon material of the first cell are formed from a common amorphous silicon material.
8. The device of claim 1 wherein the second wiring comprises a material selected from a group consisting of: silver, gold, platinum, palladium.
9. The device of claim 8 wherein the second wiring also comprises a material selected from a group consisting of: tungsten, copper, and aluminum.
10. The device of claim 1 wherein a pattern for the first switching region is not identical to a pattern for the first buffer layer region.
11. The device of claim 1 further comprising:
- a third cell, the third cell comprising a fourth wiring structure extending in the first direction overlying the first dielectric material, a third buffer layer region comprising a p+ polycrystalline silicon containing material, a third switching region comprising an amorphous silicon material, and the second wiring structure extending in the second direction orthogonal to the first direction;
- a fourth cell, the fourth cell comprising the fourth wiring structure extending in the first direction overlying the first dielectric material, a fourth buffer layer region comprising a p+ polycrystalline silicon containing material, a fourth switching region comprising an amorphous silicon material, and the third wiring structure extending in the second direction orthogonal to the first direction;
- wherein the second dielectric material is disposed at least in a region between the third switching region and the fourth switching region to electrically and physically isolate the third switching region and the fourth switching region; and
- wherein the second dielectric material is disposed at least in a region between the first switching region and the third switching region to electrically and physically isolate the first switching region and the third switching region.
12. The device of claim 1 wherein the amorphous silicon material is configured to allow metal particles from the second wiring structure to diffuse therein.
13. A method for fabricating a device including a non-volatile memory device structure, comprising:
- receiving a substrate having a surface region and comprising a plurality of transistors;
- depositing a first dielectric material overlying the surface region of the semiconductor substrate;
- forming a first cell, the first cell comprising a first wiring structure extending in a first direction overlying the first dielectric material, a first buffer layer region comprising a p+ polycrystalline silicon containing material, a first switching region comprising an amorphous silicon material, and a second wiring structure extending in a second direction orthogonal to the first direction;
- forming a second cell, the second cell comprising the first wiring structure, a second-buffer layer region comprising a p+ polycrystalline silicon containing material, a second switching region comprising an amorphous silicon material, and a third wiring structure separated from the second wiring structure and parallel to the second wiring structure; and
- forming a second dielectric material at least in a region between the first switching region and the second switching region to electrically and physically isolate the first switching region and the second switching region;
- wherein at least one transistor from the plurality of transistors is coupled to the first cell.
14. The method of claim 13 wherein forming the first cell comprises:
- forming the first wiring structure extending in the first direction overlying the first dielectric material;
- forming the first buffer layer region comprising the p+ polycrystalline silicon containing material on top of the first wiring structure;
- forming the first switching region comprising the amorphous silicon material on top of the first buffer layer region; and
- forming the second wiring structure extending in the second direction orthogonal to the first direction on top of the first switching region.
15. The method of claim 14 wherein forming the first buffer layer region comprises:
- depositing a layer of p+ polycrystalline silicon containing material on top of the first wiring structure; and
- etching away portions of the layer of p+ polycrystalline silicon containing material to form the first buffer layer region.
16. The method of claim 14 wherein forming the switching region comprises:
- depositing a layer of switching material on top of the first buffer layer region; and
- etching away portions of the layer of switching material to form the first switching region.
17. The method of claim 14 wherein forming the second wiring structure comprises:
- depositing a layer of metal on top of a portion of the first switching region; and
- etching away portions of the layer of metal to form the second wiring structure.
18. The method of claim 17 wherein the metal is selected from a group consisting of: silver, gold, platinum, palladium.
19. The method of claim 18 wherein the metal also comprises a material selected from a group consisting of: tungsten, copper, and aluminum.
20. The method of claim 17
- wherein the first buffer layer region is coupled to the first wiring structure at a first region having a first contact area;
- wherein the first switching region is coupled to the second wiring structure at a second region having a second contact area; and
- wherein the first contact area is different from the second contact area.
Type: Application
Filed: Dec 17, 2013
Publication Date: Sep 18, 2014
Applicant: Crossbar, Inc. (Santa Clara, CA)
Inventors: Scott Brad HERNER (San Jose, CA), Hagop NAZARIAN (San Jose, CA)
Application Number: 14/109,415
International Classification: H01L 27/24 (20060101); H01L 45/00 (20060101);